In fuel rails for injector-based fuel injection systems, various devices associated with the fuel system cause pressure waves in the fuel to propagate through the fuel rails. Such pressure waves, if occurring at the wrong time, may cause a reduction in the fuel being injected into the engine when the injector is pulsed open causing a lean shift condition. In certain instances, the fuel injector may have a small amount of fuel leaving the fuel rail and being injected into the engine at the time the injector is pulsed open causing a rich shift condition. In addition, such pressure waves cause noise in the system that may be objectionable. Pressure pulses will give false readings to fuel pressure regulators by operating the regulator with a false indication of fuel pressure, which may result in fuel being bypassed and returned to the fuel tank.
A known pressure dampening system uses elastic walls forming the fuel supply line. As pressure pulses occur, the elastic walls function to dampen the pressure pulsations. Other pressure dampening systems use a pressure damper plugged in the end of a fuel rail with a pressure regulator at the other end. Still other pressure dampening systems use a compliant member operable to reduce peak pressure during injector firing events. The member is positioned in the fuel rail so as to not adversely affect the flow of fuel to an injector opening in the rail. The member is not free to rotate in the rail and the member dampens the pressure pulses, which is a pair of welded together shell halves with an enclosed airspace. Other pressure dampening systems use an in-line fuel pressure damper from the outlet of the fuel filter to the fuel rail. The damper is a pressure accumulator which operative to reduce transient pressure fluctuations induced by the fuel pump and the opening and closing of the fuel injectors.
Another dampening system utilizes an integral pressure damper that is attached to the fuel rail. The return tube is brazed to the rail and then at a convenient time in the process, the damper, which is a diaphragm, is attached to the return tube and crimped into position. The diaphragm operates to reduce audible operating noise produced by the injector pressure pulsations.
Still another dampening system uses a pulse damper in the fuel pump comprising a hollow body formed of a thin walled tube of flexible and resilient plastic material with heat sealed ends forming at least one chamber. The chamber carries a compressible gas to dampen pressure pulsations. Another dampening system uses a bellows modulator inside a gear rotor fuel pump for reducing pump noise by reducing the amplitude of fuel pressure pulses. Yet another system uses a bellows-like device at the junction of the lines of the flow path of the fluid from a fuel feed pump thereby forming a discontinuity in the flow path to reduce compressional vibrations of fuel being conveyed.
Briefly, the present invention provides a fuel rail for a fuel injection system, which fuel rail can also function as a pressure damper. The fuel injection system includes a source of pressurized fuel and at least one fuel injector. The fuel rail comprises an elongated member having a longitudinal axis extending therethrough. The elongated member includes a continuous outer surface surrounding a continuous inner surface, the continuous inner surface cincturing the longitudinal axis and defining an interior volume, the continuous inner surface being exposed to the interior volume and having an uniform composition with at least one undulation disposed about the longitudinal axis
The present invention provides a method of reducing pressure pulsation in a fuel injection system having a pressurized fuel source coupled to at least one fuel injector with a fuel rail establishing fluid communication between the pressurized fuel source and the at least one fuel injector, the fuel rail extending along a longitudinal axis. In one preferred embodiment of the invention, the method is achieved by providing an elongated member that extends along the longitudinal axis, the elongated member having a continuous inner surface and a continuous outer surface of an uniform composition cincturing the longitudinal axis, the continuous inner surface defining a first predetermined internal volume of a first configuration of the fuel rail; and corrugating a first portion of the elongated member so as to define a second predetermined internal volume of a second configuration of the fuel rail.